Unloader.



F. A. HATFIELD@ H. GEARING.

UNLOADER.

APPLICATION FILED IAN. 30. 1918.

Patented Deo. 24, 1918.

NEED 'STATES FATE?? FFIQE.

FRANK A. HATFIELD AND HARRY GEARING, OF LOS ANGELES, CALIFORNIA, ASSIGN- ORS, BY DIRECT AND MESNE ASSIGNMENTS, T0 NATIONAL COMPRESSED AIR MACHINERY CO., A CORPORATION OF CALIFORNIA.

UNLQADER.

Specification of Letters Patent.

Patented. Dec.. 24, 11918..

Application filed .T annary 30. 1918. Serial No. 214,554.

To all whom t may concern.'

Be it known that We, FRANK A. HA'rriELD and HARRY GEARING, both subjects of the King of Great Britain, and both residing at Los Angeles, in the county of Los Angeles and State of California, have invented la new and useful Unloader, of which the following is a specification.

Our invention relates to compressed air machinery, and more particularly to an unloader for use with an air compressor. Where an air compressor is connected to a receiver and is allowed to operate continuously it is often desirable to disconnect the compressor from the receiver whenever the air in the receiver reaches a predetermined pressure, thus preventing the production of excessive pressures in the receiver and relieving the compressor of its load so that power is conserved.

The principal object of our invention is 'to provide a new and useful form of unloader which will disconnect the compressor from the receiver without interrupting the tiow of air from the compressor and without allowing an appreciable amount of air to escapo from the receiver during the operation.

Further objects and advantages will be made evident hereinafter.

Referring to the drawings which are for illustrative purposes only,

'Figure l isa somewhat diagramn'iatic view showing our invention applied to an air compressor and receiver.

Fig. 2 is a vertical section on the central line of the unloader showing the pilot valve attached thereto.

Fig. 3 is a similar section on a plane at right angles to the section of Fig. 2.

Fig. 4 is a section on a plane represented by the line 4-4 of Fig. 3.

In the form of our invention illustrated in the drawings, an unloader 11 is used in combination with an air compressor 12 and a receiver 13, a pilot. valve 14 being applied to the unloader for the purpose of governing its action.

The unloader consists of a. valve body 21 to which is attached an operating cylinder 22. vFormed in the valve body 21 is an upper chamber 23 which is in open conimunication through a central passage 24 formed in the operating cylinder 22 with a Working chamber 25, also formed in the cylinder 22. Formed on the valve body 21 and projecting into the upper chamber 23 is an upper seat 26, and similarly formed on the cylinder 22, projecting into the passage 24, is a lower seat 27. Between the seats 26 and 27 is a machined cylindrical opening hereinafter called the piston valve cylinder 28. Surrounding Ithe piston valve cylinder 28 is a central annular port 29 communieating with an annular pressure opening 30 which surrounds the piston valve cylinder concentrically. Opening into the pressure opening 30 is a. pressure pipe 3l. Opening into the upper chamber 23 is a receiver pipe 32, and openingA into the passage 24 is an exhaust pipe 33.

Sliding in the pistonvalve cylinder 28 is a main piston valve 35, this valve having a central cavity 36 which is connected to an inlet opening 37 cut in the side of the piston valve. Secured in the top of the piston valve 35 is a valve plug 39, this plug having a series of holes 40 communicatingwith a central cavity 41 formed therein in which is placed a feather valve spring 42. This feather valve spring is under compression and operates against an auxiliary feather valve 43 which is formed of flat metal having upturned edges 44 which iit loosely on the periphery of the valve plug 39. Cut in the periphery of this plug above the edges 44 is a plurality of holes 45.

Located adjacent to the lower seat 27 and formed integrally with the cylinder 24 is a spider 47. Passing through this spider and connected with the piston valve is a piston rod 48 to the lower end of which a piston 49 is attached, this piston sliding freely in the working chamber 25 and being provided with cup leathers 50 so that it makes an air-tight joint therewitli. Surrounding the piston rod 4S is a spring 51 which is under compression and which presses at one end against the spider 42 and at the other end against the piston 49 thus tending to hold the piston 49 and the valve 35 in its lower position as shown.

Closing the bottom of the working chamber 25 is a cylinder cover 51 which is secured to the cylinder 22 by means of bolts 52 and which has a by-pass opening 55% formed therein. rlhe by-pass opening 53 is connected through a by-pass pipe 54 and a.

by-pass valve 55 with a receiver pipe 56.

This receiver pipe 56 is connected into the receiver pipe 32 and both of these pipes are connected through a pipe 57 with the receiver 13.

The cylinder cover 51 also has a central openine 60 into which the pilot valve 14 is secure. The pilot valve 14 forms no part of the present invention, being` of a form well known in the art, for which any other well known forni may be substituted without departing from the spirit of my invention. Its construction will therefore not be described, its operation being exactly similar to that of many others of similar type.

The method of operation is as follows:

The air compressor 12 being actuated from any source of power not shown, air under pressure is delivered to the pipe 31 into the pressure opening 30 and through the port 29 into the piston valve cylinder 28, passing readily into the upper chamber Y 23 and through the pipes 32 and 5T into the receiver 13. The pipe 56 being also connected to the receiver 13, air under pressure is admitted to the pilot valve 14, the Vvalve being closed. rl`he pilot valve 14 is so arranged thatI no air is allowed to pass through the openings 60 into the space below the piston 49 until the pressure in the receiver reaches a predetermined value. `Whenever this predetermined value is reached the pilot valve 14 opens allowing air under pressure to pass from the receivei- 13 into the space below the piston 49. The full air pressure of the receiver is therefore eX- erted on the piston 49, forcing it upwardly against the tension of the spring 5l. The main piston valve 35 is therefore raised from the lower seat 2T. being forced upwardly toward the seat 26. The feather valve 44 is normally held in its extreme lower position on its seat. by means of the spring 42. As the piston valve moves upwardly, however, its upper edge closes the communication between t-he opening 29 and the upper portion of the piston valve cylinder 28 at the saine time keeping closed all communication between the opening 29 and the passage 24. In other words the main piston valve 35 completely closes the port 29 so that air can.

not pass above or below it for a short interval during the central portion of its stroke.. The main piston valve 35 is so constructed, however, that at the instant the port 29 is closed the opening 37 is in open communication with that port. Air under pressure therefore passes through the opening 37 to the cavity 36, lifting the auxiliary feather valve 43 from its seat and allowing the air under pressure to pass through the holes 45 and the holes 40 into the upper portion of the piston valve chamber 28. There is therefore no interruption on the flow of air from the pipe 31 and dangerous piessures are not built up in the piping system due to the complete shutting off of the compressor pressure.

'As the piston valve continues to rise, the opening 37 is gradually sluit off, but not until the piston valve has risen sufficiently to allow air to flow downwardly thereunder into the passage 24. As soon as the air starts to flow freely into the passage 24 thel receiver pressure, working backward through the pipe 32 and through the openings 40 and 45 assisted by the spring 42, forces the feather valve 43 back on its seat so that there is no appreciable loss in receiver pressure duiiiig the movement of the piston valve 35. The piston valve 35 finally seats on the upper seat 26, the compressor working through the pipe 31 and through the openings in the spider 47 into the passage 24 and from thence into the exhaust pipe 33 which is at or near atmospheric pressure.

When operating` in this manner there is almost no load on the air compressor, which continues to operate without load `until the receiver pressure drops sufficiently to operate the pilot valve 14. y rlhe operation of the pilot valve 14 releases the pressure from below the piston 49 and allows the piston 49 to be forced downwardly by the spring 51, the piston` valve 35 being also lowered so that the pipe 31 is connected to the pipe 32 and the load is again placed on the compressor and the receiver pressure is again raised.

'Should the compressor be shut down for any reason, it is desirable to start it without load even if the receiver pressure is quite high. In this case the valve 55 is opened admitting the full receiver pressure to the bottom of the piston 49 and forcing the piston valve 35 up so that the pipe 31 and the pipe 33 are connected. The compressor may then be started and whenever it has reached its full speed the valve 55 may be closed thus allowing the piston to drop and to reconnect the compressor with the receiver.

What we claim is 1. In an unloader a valve Ebody having a piston valve cylinder therein, said valve body having a central port opening into said cylinder; a main piston valve fitting in gas tight relationship in said cylinder, said valve being of sufficient length and so arranged as to entirely close said port at an intermediate position in its travel; means for supplying gas under pressure to said port; a receiver pipe connected into the space above said main piston valve, the space below said main piston valve being connected with the atmosphere; and an auX- iliary valve so placed as to allow air to pass from said port. to said receiver pipe during the time said port is closed by said piston valve.

2. A combination as in claim 1 in which nasceva 5. A combination as in claim 4 alsocomprising a valve plug secured in'the top of said auxiliary valve opening, said valve plug having a central cavity in open communication with the space above said piston valve; and a valve spring in said cavity, Said auxiliary valve being in the form of a flat plate having upturned edges tting decided upon value.

around the lower end of said valve plug, said valve plug having va series of holes cut therein above the upturned edges of said auxiliary Valve.

6. In an unloader, a valve body.; a pressure pipe connected into said valve body; a re-4 ceiver pipe connected into said valve body; an exhaust pipe connected into said valve body; a main valve 'so arranged to connect either said receiver pipe or said exhaust pipe With said pressure pipe; and pressure controlled means for actuating said main valve. y 7. In an unloader,avalve body; apressure pipe connected into said valve body; a receiver pipe connected into said valve body; an exhaust pipe connected into Said valve body; a main valve so arranged to connect either said receiver pipe or said exhaust pipe with said pressure pipe; a spring arranged to normally hold said main valve in such a position that said presure pipe is connected to said receiver pipe; and pressure controlled means for forcing said main valve from said normal position into such a position that said pressure pipe is connected to said exhaust pipe.

8. In an unloader, a valve body; a pressure pipe connected into said valve body; a receiver pipe connected into said valave body; an exhaust pipe connected into said valve body; a main valve so arranged to connect either said receiver pipev or said exhaust pipe with said pressure pipe; a spring a-rranged to normally hold `said main valve inv such a position that said pressure pipe is connected to said receiver pipe; a, piston for forcing said main valve from sald normal position in such a position that said pressure pipe is connected to said exhaust pipe; and a pilot valve so constructed as to admlt air pressure to said piston Whenever the pressure in said receiver pipe exceeds a certain pre- 9. A combination as in claim 7 in Which said main valve is so constructed that said pressure pipe is disconnected from 'said receiver pipe before being connected to said exhaust pipe.

10. A combination as in claim 9 Which also includes an auxiliary valve so arranged as to relieve excess pressure in said pressure pipe during the time said main valve is in motion.

11. A combination as in claim 10 Which also includes means for .delivering any air passing through said auxiliary valve to said receiver. y

In testimony whereof, We have hereunto set our hands and seals this 17th da of January, 19177 at Los Angeles, California.

FRANK A. HATFELD. HARRY GEARING. 

